The invention relates generally to power-driven conveyors and, more particularly, to conveyors having retractable stops to selectively accumulate and release conveyed articles.
Conveyors are used in industrial applications to transport articles from one processing station to another. Often a continuously moving conveyor is used to deliver articles to a downstream processing station. As soon as the supply of articles exceeds the handling capacity of the downstream processing station, a stop mechanism is moved into position to block the articles at a position on the conveyor upstream of the processing station. Friction between the conveying surface and the backed-up, or accumulated, articles causes the articles to push against each other. The pressure exerted against the articles at the front of the group of accumulated articles is called back line pressure. As more articles back up, the back line pressure increases. Back line pressure can cause damage to the articles, excessively load the conveyor belt and its drive components, and accelerate belt wear. Even when the conveyor includes freely rotatable rollers to reduce friction, the pressure from a large number of backed-up products can be significant. And, when the stop mechanism, which is typically a flat plate, is moved into the blocking position and, especially, out of the blocking position, it slides on the articles at the head of the accumulation. The sliding friction of the stop mechanism against the articles can scratch or otherwise damage their surfaces or labels as the stop mechanism retracts to release the accumulated articles.
Thus, there is a need for a conveyor that can accumulate and release conveyed articles without damaging accumulated articles or damaging their surfaces.